Not Applicable
Not Applicable
The present invention is related to communication protocols in computer networks, and particularly to reliability protocols for error control in dynamic and heterogeneous computer networks.
Communications protocols for transmitting a sequence of data units from a first application to a second application via a source device, intermediate network routing devices, and a destination device in a computer network are known. xe2x80x9cReliablexe2x80x9d protocols provide for detection and retransmission of data units that are lost in transit. In an xe2x80x9cend-to-endxe2x80x9d reliable protocol the destination device is responsible for detecting the loss of data units. The order of transmission of the data units is maintained by delaying transmission of data units that are received after the loss of a data unit is detected by the destination device. In particular, the data units are buffered at the destination device until the lost data unit is received by the destination device. The source device retransmits the lost data unit to the destination device after being notified of the loss via a repair request message. In a xe2x80x9chop-by-hopxe2x80x9d reliable protocol the destination device and intermediate network devices are responsible for detecting the loss of data units. As in the end-to-end protocol, the order of transmission of the data units is maintained by delaying transmission of data units that are received after the loss is detected. In particular, the data units are buffered at the device that recognized the loss. The lost data unit may be retransmitted by either the source device or an intermediate repair head device. In a xe2x80x9cdatagramxe2x80x9d protocol, which is not a reliable protocol, lost data units are not retransmitted and the order of transmission of the data units is not necessarily maintained. Each of these known protocols performs well under some circumstances and poorly under other circumstances.
One limitation associated with the sequenced reliable protocol is that data forwarding is held up until the lost packet is successfully received. This can significantly reduce the useful data rate of the flow and increase unnecessary transmissions, particularly in environments with large bandwidth-product delays. This is counterproductive for applications that benefit from reliability but can tolerate out-of-sequence delivery.
One limitation associated with the datagram protocol is that loss of data units is not detected and repaired. Some applications are intolerant to data unit loss. Further, the order of transmission of the data units is not necessarily maintained. Some applications are sensitive to the order in which data units are delivered. Also, the application may need, or benefit from, limited reliability which is still better than the current Internet best-effort service.
In accordance with the present invention, new reliability management protocols are employed to provide more efficient operation in dynamic and heterogeneous networking environments. These protocols present a range of levels of error control and sequence order control.
The new protocols include a reliable protocol, a semireliable protocol and an acknowledgement-based semi-reliable protocol. In the reliable protocol the order of transmission of the data units is not necessarily maintained and lost data units are identified and retransmitted. In the semi-reliable protocol the order of transmission of the data units is not necessarily maintained and limited action is taken to identify and recover lost data units. In the acknowledgement based semi-reliable protocol the receiver device in a link acknowledges receipt of each data unit by sending an acknowledgement message to the transmitter device, and the transmitter device is responsible for detecting the loss of data units.